I would hope Mule Deer will chime in on this subject, especially in relation to a rifle that has been properly cleaned down to bare steel and then Dyna Bore coated.
I believe he has stated in the past that while the company used to say no phosphor bronze bore brushes they then said it was ok, their dyna bore coating could withstand it???
Of course they have no customer service/support anymore so you can't find out from them.
And as stated above bore scope is the way to go in accurately judging how clean your barrel is.
I waited until this thread went down several apparently inevitable rat-holes to comment:
Haven't used bore brushes of any kind very often for years now. The biggest use I get out of them is wrapping one with a cotton patch to measure rifling twist.
Between excellent oil-based bore solvents such as Wipe-Out and Montana X-Treme, have never seen much need to brush bores. This includes not just to remove copper fouling but powder fouling--what little there is from today's cleaner-burning powders.
Also, my experience is that Dan Lilja's opinion that attempting to remove ALL powder-fouling is detrimental to accuracy. Dan came to this conclusion after lots of testing. And in my nearly 20 years with a Gradient Hawkeye bore-scope, he's exactly right.
